Compound semiconductors and their application

ABSTRACT

Disclosed are new compound semiconductors which may be used for solar cells or as thermoelectric materials, and their application. The compound semiconductor may be represented by a chemical formula: In x Co 4 Sb 12-z Te z , where 0&lt;x≦0.5 and 0.8&lt;z≦2.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/KR2012/003255 filed on Apr. 26, 2012, which claims priority toKorean Patent Application No. 10-2011-0040401 filed on Apr. 28, 2011 andKorean Patent Application No. 10-2012-0043839 filed on Apr. 26, 2012 inthe Republic of Korea, the entire contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present disclosure relates to a new compound semiconductor materialwhich may be used for solar cells or as thermoelectric materials, itspreparation method, and its applications.

BACKGROUND ART

A compound semiconductor is not a single element such as silicon andgermanium but a compound having two or more kinds of combined elementsserving as a semiconductor. Various kinds of compound semiconductorshave been developed and used in many fields. For example, a compoundsemiconductor may be used for thermoelectric conversion devices using aPeltier effect, light emitting devices such as light emitting diodes andlaser diodes using a photoelectric conversion effect, solar cells, orthe like.

Among these, the thermoelectric conversion device may be applied tothermoelectric conversion generation, thermoelectric conversion coolingor the like. Here, in the thermoelectric conversion generation, athermal electromotive force generated by applying a temperaturedifference to the thermoelectric conversion device is used forconverting thermal energy to electric energy.

The energy conversion efficiency of the thermoelectric conversion devicedepends on ZT which is a performance index of the thermoelectricconversion material. Here, ZT is determined according to a Seebeckcoefficient, electric conductivity, thermal conductivity, or the like.In more detail, ZT is proportional to the square of the Seebeckcoefficient and the electric conductivity and is inversely proportionalto the thermal conductivity. Therefore, in order to enhance the energyconversion efficiency of the thermoelectric conversion device,development of a thermoelectric conversion material with a high Seebeckcoefficient, a high electric conductivity, or a low thermal conductivityis desired.

Meanwhile, a solar cell is environment-friendly since it does not needan energy source other than solar rays, and therefore are activelystudied as an alternative future energy source. A solar cell may begenerally classified as a silicon solar cell using a single element ofsilicon, a compound semiconductor solar cell using a compoundsemiconductor, and a tandem solar cell where at least two solar cellshaving different band gap energies are stacked.

Among these, a compound semiconductor solar cell uses a compoundsemiconductor in a light absorption layer which absorbs solar rays andgenerates an electron-hole pair, and may particularly use compoundsemiconductors in the III-V group such as GaAs, InP, GaAlAs and GaInAs,compound semiconductors in the I-III-VI group such as CdS, CdTe and ZnS,and compound semiconductors in the group represented by CuInSe₂.

The light absorption layer of the solar cell demands excellent long-termelectric and optical stability, high photoelectric conversionefficiency, and easy control of the band gap energy or conductivity bycomposition change or doping. In addition, conditions such as productioncost and yield should also be met for practical use. However, manyconventional compound semiconductors fail to meet all of theseconditions at once.

DISCLOSURE Technical Problem

The present disclosure is designed to solve the problems of the priorart, and therefore it is an object of the present disclosure to providea new compound semiconductor material, which may be utilized in variousways for thermoelectric conversion materials of thermoelectricconversion devices, solar cells or the like, a preparation methodthereof, and a thermoelectric conversion device or solar cell using thesame.

Other objects and advantages of the present disclosure will beunderstood from the following descriptions and become apparent by theembodiments of the present disclosure. In addition, it is understoodthat the objects and advantages of the present disclosure may beimplemented by components defined in the appended claims or theircombinations.

Technical Solution

In one aspect, after repeated studies of a compound semiconductor,inventors of the present disclosure have successfully synthesized acompound semiconductor represented by Chemical Formula 1, and found thatthis compound can be used for a thermoelectric conversion material of athermoelectric conversion device or a light absorption layer of a solarcell.

Chemical Formula 1

In_(x)Co₄Sb_(12-z)Te_(z)

where, in the Chemical Formula 1, 0<x≦0.5 and 0.8<z≦2.

Preferably, in Chemical Formula 1, 0<x≦0.4.

Also preferably, in Chemical Formula 1, 0.9<z≦2.

Also preferably, in Chemical Formula 1, 0.9<z≦1.75.

More preferably, in Chemical Formula 1, 1.0≦z≦1.5.

In another aspect, the present disclosure also provides a preparationmethod of a compound semiconductor, which includes: mixing In, Co, Sband Te; and thermally treating the mixture obtained in the mixing step,thereby preparing the compound semiconductor defined in claim 1.

Preferably, in the preparation method of a compound semiconductor, thethermally treating step is performed at 400° C. to 800° C.

Also preferably, the thermally treating step includes at least twothermal treatment stages.

In another aspect, the present disclosure also provides a thermoelectricconversion device, which includes the compound semiconductor as above.

In another aspect, the present disclosure also provides a solar cell,which includes the compound semiconductor as above.

Advantageous Effects

According to the present disclosure, a new compound semiconductormaterial is provided.

In one aspect, the new compound semiconductor may replace a conventionalcompound semiconductor or may be used as another material in addition tothe conventional compound semiconductor.

Further, in one aspect of the present disclosure, since the compoundsemiconductor has good thermoelectric conversion performance, it may beused for a thermoelectric conversion device.

In addition, in another aspect of the present disclosure, the compoundsemiconductor may be used for a solar cell. Particularly, the compoundsemiconductor of the present disclosure may be used as a lightabsorption layer of the solar cell.

Moreover, in another aspect of the present disclosure, the compoundsemiconductor may be used for an IR window or IR sensor whichselectively passes IR, a magnetic device, a memory or the like.

DESCRIPTION OF DRAWINGS

Other objects and aspects of the present disclosure will become apparentfrom the following descriptions of the embodiments with reference to theaccompanying drawings in which:

FIG. 1 is a graph showing thermal conductivity values according to atemperature change of compound semiconductors according to an exampleaccording to the present disclosure and a comparative example; and

FIG. 2 is a graph showing ZT values according to a temperature change ofcompound semiconductors according to the example according to thepresent disclosure and the comparative example.

PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. Priorto the description, it should be understood that the terms used in thespecification and the appended claims should not be construed as limitedto general and dictionary meanings, but interpreted based on themeanings and concepts corresponding to technical aspects of the presentdisclosure based on the principle that the inventor is allowed to defineterms.

Therefore, the description proposed herein is just a preferable examplefor the purpose of illustration only, and is not intended to limit thescope of the disclosure, so it should be understood that otherequivalents and modifications could be made thereto without departingfrom the spirit and scope of the disclosure.

The present disclosure provides a new compound semiconductor representedby Chemical Formula 1 below.

Chemical Formula 1

In_(x)Co₄Sb_(12-z)Te_(z)

where, in the Chemical Formula 1, 0<x≦0.5 and 0.8<z≦2.

Preferably, in Chemical Formula 1, x may satisfy the condition: 0<x≦0.4.

More preferably, in Chemical Formula 1, x may satisfy the condition:0<x≦0.25.

At this time, x may be 0.25. In this case, Chemical Formula 1 may berepresented by In_(0.25)Co₄Sb_(12-z)Te_(z). Here, 0.8<z≦2.

Also preferably, in Chemical Formula 1, z may satisfy the condition:0.85<z≦2. Also preferably, in Chemical Formula 1, z may satisfy thecondition: 0.9<z≦2.

Also preferably, in Chemical Formula 1, z may satisfy the condition:0.95<z≦2.

More preferably, in Chemical Formula 1, z may satisfy the condition:0.85<z≦1.75. More preferably, in Chemical Formula 1, z may satisfy thecondition: 0.9<z≦1.75.

More preferably, in Chemical Formula 1, z may satisfy the condition:0.95<z≦1.75. More preferably, in Chemical Formula 1, z may satisfy thecondition: 1.0≦z≦1.5.

Particularly, in Chemical Formula 1, z may be 1.5.

The compounds described above are known as skutterudites. The compoundshave a crystal structure that comprises a simple cubic lattice structureto form a cubic unit cell. Meanwhile, the compound semiconductorrepresented by Chemical Formula 1 may include a secondary phasepartially, and the amount of the secondary phase may vary depending on athermal treatment condition.

A preparation method of a compound semiconductor represented by ChemicalFormula 1 according to the present disclosure may include: forming amixture containing In, Co, Sb and Te; and thermally treating themixture.

At this time, each material used in the mixture forming step may be in apowder form, but the present disclosure is not limited to a specificform of the material.

Preferably, the thermally treating step may be performed in vacuum or ina gas such as Ar, He and N₂, partially containing hydrogen or notcontaining hydrogen.

At this time, the thermally treating temperature may be 400° C. to 800°C. Preferably, the thermally treating temperature may be 450° C. to 700°C. More preferably, the thermally treating temperature may be 500° C. to650° C.

Meanwhile, the thermally treating step may include at least two thermaltreatment stages. For example, a first thermal treatment may beperformed at a first temperature to the mixture obtained in the mixtureforming step, namely in the step of mixing materials, and a secondthermal treatment may be performed thereto at a second temperature.

Here, some of the thermal treatment stages may be performed during themixture forming step where materials are mixed is executed.

For example, the thermally treating step may include three thermaltreatment stages composed of a first thermal treatment stage, a secondthermal treatment stage and a third thermal treatment (sintering) stage.In addition, the first thermal treatment stage may be performed in atemperature range of 400° C. to 600° C., and the second and thirdthermal treatment stages may be performed in a temperature range of 600°C. to 800° C. The first thermal treatment stage may be performed duringthe mixture forming step, and the second and third thermal treatmentstages may be performed in order after the mixture forming step.

A thermoelectric conversion device according to the present disclosuremay include the compound semiconductor described above. In other words,the compound semiconductor according to the present disclosure may beused as a thermoelectric conversion material for the thermoelectricconversion device. Particularly, the compound semiconductor according tothe present disclosure has a large ZT value, which is a performanceindex of the thermoelectric conversion material. In addition, due to lowthermal conductivity, a high Seebeck coefficient and high electricconductivity, the compound semiconductor has excellent thermoelectricconversion performance. Therefore, the compound semiconductor accordingto the present disclosure may replace a conventional thermoelectricconversion material or may be used for a thermoelectric conversiondevice in addition to the conventional compound semiconductor.

In addition, a solar cell according to the present disclosure mayinclude the compound semiconductor above. In other words, the compoundsemiconductor according to the present disclosure may be used for asolar cell, particularly as a light absorption layer of the solar cell.

The solar cell may be produced in a structure where a front surfacetransparent electrode, a buffer layer, a light absorption layer, a rearsurface electrode and a substrate are laminated in order from the sidewhere a solar ray is incident. The substrate located at the lowestportion may be made of glass, and the rear surface electrode on theentire surface thereof may be formed by depositing metal such as Mo.

Subsequently, the compound semiconductor according to the presentdisclosure may be laminated on the rear surface electrode by means of anelectron beam deposition method, a sol-gel method, or a PLD (PulsedLaser Deposition) to form the light absorption layer. On the lightabsorption layer, a buffer layer for buffering the difference in latticeconstants and band gaps between a ZnO layer serving as the front surfacetransparent electrode and the light absorption layer may be present. Thebuffer layer may be formed by depositing a material such as CdS by meansof CBD (Chemical Bath Deposition) or the like. Next, the front surfacetransparent electrode may be formed on the buffer layer by means ofsputtering or the like as a ZnO film or a ZnO and ITO laminate.

The solar cell according to the present disclosure may be modified invarious ways. For example, it is possible to manufacture a tandem solarcell where a solar cell using the compound semiconductor according tothe present disclosure as the light absorption layer is laminated. Inaddition, the solar cell laminated as described above may employ a solarcell using silicon or another known compound semiconductor.

In addition, it is possible to change a band gap of the compoundsemiconductor according to the present disclosure and laminate aplurality of solar cells which use compound semiconductors havingdifferent band gaps as the light absorption layer. The band gap of thecompound semiconductor according to the present disclosure may beadjusted by changing a composition ratio of a component of the compound,particularly Te.

In addition, the compound semiconductor according to the presentdisclosure may also be applied to IR windows or IR sensors whichselectively pass IR.

EXAMPLES

Hereinafter, embodiments of the present disclosure will be described indetail. The embodiments of the present disclosure, however, may takeseveral other forms, and the scope of the present disclosure should notbe construed as being limited to the following examples. The embodimentsof the present disclosure are provided to more fully explain the presentdisclosure to those having ordinary knowledge in the art to which thepresent disclosure pertains.

Example 1

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having a composition of In_(0.25)Co₄Sb₁₁ in a pelletform. The mixture was heated at 500° C. for 15 hours under H₂ (1.94%)and N₂ gas. The time for raising the temperature to 500° C. was 1 hourand 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₁₁ as a reagent to make anIn_(0.25)Co₄Sb₁₁Te₁ mixture. The mixture was prepared in a glove bagfilled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. The time forraising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb₁₁Te₁ powder was obtained.

A part of the composed materials prepared above was formed into acylinder having a diameter of 4 mm and a length of 15 mm, and anotherpart was formed into a disk having a diameter of 10 mm and a thicknessof 1 mm. After that, a pressure of 200 MPa was applied thereto by usinga CIP (Cold Isostatic Pressing). Subsequently, the obtained result wasput into a quartz tube and vacuum-sintered for 12 hours.

In regard to the sintered disk, thermal conductivity (κ) of the materialprepared above was measured by using TC-7000 (Ulvac-Rico, Inc) atpredetermined temperature intervals. The measurement result is shown inFIG. 1 as Example 1.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals. In addition, aZT value was calculated by using each measured value. The calculationresult is shown in FIG. 2 as Example 1.

Example 2

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having compositions of In_(0.25)Co₄Sb₁₀ andIn_(0.25)Co₄Sb₁₁ in a pellet form. The mixture was heated at 500° C. for15 hours under H₂ (1.94%) and N₂ gas. The time for raising thetemperature to 500° C. was 1 hour and 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₁₀ as a reagent to make anIn_(0.25)Co₄Sb₁₀Te₂ mixture. In addition, this mixture was suitablymixed with the In_(0.25)Co₄Sb₁₁ to make anIn_(0.25)Co₄Sb_(10.75)Te_(1.25) mixture. The mixture was prepared in aglove bag filled with Ar.

The materials mixed as above were put in a silica tube andvacuum-sealed, and then were heated at 650° C. for 36 hours. The timefor raising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb_(10.75)Te_(1.25) powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP.Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In regard to the sintered disk, thermal conductivity (κ) of the materialprepared above was measured by using TC-7000 (Ulvac-Rico, Inc). Themeasurement result is shown in FIG. 1 as Example 2.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals. In addition, aZT value was calculated by using each measured value. The calculationresult is shown in FIG. 2 as Example 2.

Example 3

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having compositions of In_(0.25)Co₄Sb₁₃ andIn_(0.25)Co₄Sb₁₁ in a pellet form. The mixture was heated at 500° C. for15 hours under H₂ (1.94%) and N₂ gas. The time for raising thetemperature to 500° C. was 1 hour and 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₁₀ as a reagent to make anIn_(0.25)Co₄Sb₁₀Te₂ mixture. In addition, the mixture was suitably mixedwith the In_(0.25)Co₄Sb₁₁ to make an In_(0.25)Co₄Sb_(10.5)Te_(1.5)mixture. The mixture was prepared in a glove bag filled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. Here, thetemperature rising time was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb_(10.5)Te_(1.5) powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP.

Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In regard to the sintered disk, thermal conductivity (κ) of the materialprepared above was measured by using TC-7000 (Ulvac-Rico, Inc). Themeasurement result is shown in FIG. 1 as Example 3.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals. In addition, aZT value was calculated by using each measured value. The calculationresult is shown in FIG. 2 as Example 3.

Example 4

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having a composition of In_(0.25)Co₄Sb₁₀ in a pelletform. The mixture was heated at 500° C. for 15 hours under H₂ (1.94%)and N₂ gas. The time for raising the temperature to 500° C. was 1 hourand 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₁₀ as a reagent to make anIn_(0.25)Co₄Sb₁₀Te₂ mixture. The mixture was prepared in a glove bagfilled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. Here, the timefor raising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb₁₀Te₂ powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP.

Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In regard to the sintered disk, thermal conductivity (κ) of the materialprepared above was measured by using TC-7000 (Ulvac-Rico, Inc). Themeasurement result is shown in FIG. 1 as Example 4.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals. In addition, aZT value was calculated by using each measured value. The calculationresult is shown in FIG. 2 as Example 4.

Comparative Example 1

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having a composition of In_(0.25)Co₄Sb₁₂ in a pelletform.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours, andIn_(0.25)Co₄S₁₂ powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP (ColdIsostatic Pressing). Subsequently, the obtained result was put into aquartz tube and vacuum-sintered for 12 hours.

In addition, in regard to the sintered disk, thermal conductivity (κ) ofthe material prepared above was measured by using TC-7000 (Ulvac-Rico,Inc), similar to Examples. The measurement result is shown in FIG. 1 asComparative Example 1.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals, similar toExamples. In addition, a ZT value was calculated by using each measuredvalue. The calculation result is shown in FIG. 2 as Comparative Example1.

Comparative Example 2

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having compositions of In_(0.25)Co₄Sb₁₂ andIn_(0.25)Co₄Sb₁₁ in a pellet form. In addition, as making H₂ (1.94%) andN₂ gas flow thereto, the mixture was heated at 500° C. for 15 hours. Thetime for raising the temperature to 500° C. was 1 hour and 30 minutes.Next, Te was added to In_(0.25)Co₄Sb₁₁ as a reagent to make anIn_(0.25)Co₄Sb₁₁Te₁ mixture. In addition, this mixture was suitablymixed with the In_(0.25)Co₄Sb₁₂ to make anIn_(0.25)Co₄Sb_(11.75)Te_(0.25) mixture. The mixture was prepared in aglove bag filled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. Here, the timefor raising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb_(11.75)Te_(0.25) powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm.

After that, a pressure of 200 MPa was applied thereto by using a CIP.Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In addition, in regard to the sintered disk, thermal conductivity (κ) ofthe material prepared above was measured by using TC-7000 (Ulvac-Rico,Inc), similar to the Examples. The measurement result is shown in FIG. 1as Comparative Example 2.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals, similar toExamples. In addition, a ZT value was calculated by using each measuredvalue. The calculation result is shown in FIG. 2 as Comparative Example2.

Comparative Example 3

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having compositions of In_(0.25)Co₄Sb₁₂ andIn_(0.25)Co₄Sb₁₁ in a pellet form. In addition, the mixture was heatedat 500° C. for 15 hours under H₂ (1.94%) and N₂ gas. The time forraising the temperature to 500° C. was 1 hour and 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₁₁ as a reagent to make anIn_(0.25)Co₄Sb₁₁Te₁ mixture. In addition, this mixture was suitablymixed with the In_(0.25)Co₄Sb₁₂ to make an In_(0.25)Co₄Sb_(11.5)Te_(0.5)mixture. The mixture was prepared in a glove bag filled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. Here, the timefor raising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb_(11.5)Te_(0.5) powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm.

After that, a pressure of 200 MPa was applied thereto by using a CIP.Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In addition, in regard to the sintered disk, thermal conductivity (κ) ofthe material prepared above was measured by using TC-7000 (Ulvac-Rico,Inc), similar to Examples. The measurement result is shown in FIG. 1 asComparative Example 3.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals, similar toExamples. In addition, a ZT value was calculated by using each measuredvalue. The calculation result is shown in FIG. 2 as Comparative Example3.

Comparative Example 4

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having compositions of In_(0.25)Co₄Sb₁₂ andIn_(0.25)Co₄Sb₁₁ in a pellet form. In addition, the mixture was heatedat 500° C. for 15 hours under H₂ (1.94%) and N₂ gas. The time forraising the temperature to 500° C. was 1 hour and 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₁₁ as a reagent to make anIn_(0.25)Co₄Sb₁₁Te₁ mixture. In addition, the mixture was suitably mixedwith the In_(0.25)Co₄Sb₁₂ to make an In_(0.25)Co₄Sb_(11.25)Te_(0.75)mixture. The mixture was prepared in a glove bag filled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. The time forraising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb_(11.25)Te_(0.75) powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP.Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In addition, in regard to the sintered disk, thermal conductivity (κ) ofthe material prepared above was measured by using TC-7000 (Ulvac-Rico,Inc), similar to Examples. The measurement result is shown in FIG. 1 asComparative Example 4.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals, similar toExamples. In addition, a ZT value was calculated by using each measuredvalue. The calculation result is shown in FIG. 2 as Comparative Example4.

Comparative Example 5

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having compositions of In_(0.25)Co₄Sb₉ andIn_(0.25)Co₄Sb₁₀ in a pellet form. In addition, the mixture was heatedat 500° C. for 15 hours under H₂ (1.94%) and N₂ gas. The time forraising the temperature to 500° C. was 1 hour and 30 minutes.

Next, Te was added to In_(0.25)Co₄Sb₉ as a reagent to make anIn_(0.25)Co₄Sb₉Te₃ mixture. In addition, the mixture was suitably mixedwith the In_(0.25)Co₄Sb₁₀ to make an In_(0.25)Co₄Sb_(9.5)Te_(2.5)mixture . The mixture was prepared in a glove bag filled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. Here, the timefor raising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb_(9.5)Te_(2.5) powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP.Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In addition, in regard to the sintered disk, thermal conductivity (κ) ofthe material prepared above was measured by using TC-7000 (Ulvac-Rico,Inc) at predetermined temperature intervals. The measurement result isshown in FIG. 1 as Comparative Example 5.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals. In addition, aZT value was calculated by using each measured value. The calculationresult is shown in FIG. 2 as Comparative Example 5.

Comparative Example 6

In, Co and Sb were prepared as reagents, and were mixed by using mortarto make a mixture having a composition of In_(0.25)Co₄Sb₉ in a pelletform. In addition, the mixture was heated at 500° C. for 15 hours underH₂ (1.94%) and N₂ gas. The time for raising the temperature to 500° C.was 1 hour and 30 minutes.

Next, Te was added to IN_(0.25)Co₄Sb₉ as a reagent to make anIn_(0.25)Co₄Sb₉Te₃ mixture. The mixture was prepared in a glove bagfilled with Ar.

The materials mixed as above were put into a silica tube andvacuum-sealed and then heated at 650° C. for 36 hours. Here, the timefor raising the temperature to 650° C. was 1 hour and 30 minutes, andIn_(0.25)Co₄Sb₉Te₃ powder was obtained.

A part of the material prepared above was formed into a cylinder havinga diameter of 4 mm and a length of 15 mm, and another part was formedinto a disk having a diameter of 10 mm and a thickness of 1 mm. Afterthat, a pressure of 200 MPa was applied thereto by using a CIP.

Subsequently, the obtained result was put into a quartz tube andvacuum-sintered for 12 hours.

In addition, in regard to the sintered disk, thermal conductivity (κ) ofthe material prepared above was measured by using TC-7000 (Ulvac-Rico,Inc) at predetermined temperature intervals. The measurement result isshown in FIG. 1 as Comparative Example 6.

In regard to the sintered cylinder, electric conductivity and a Seebeckcoefficient of the material prepared above were measured by using ZEM-3(Ulvac-Rico, Inc) at predetermined temperature intervals. In addition, aZT value was calculated by using each measured value. The calculationresult is shown in FIG. 2 as Comparative Example 6.

First, referring to the results shown in FIG. 1, it could be found thatthe compound semiconductors according to Examples 1 to 4 of the presentdisclosure have lower thermal conductivity over the entire temperaturemeasurement region in comparison to the compound semiconductorsaccording to Comparative Example 1 to 6.

Further, in Examples 1 to 3, it could be found that thermal conductivityis greatly lowered in the case where z has a range of 1.0≦z≦1.5, andparticularly thermal conductivity is remarkably lowered in Example 3where z=1.5.

In addition, if the ZT value of each material prepared above is lookedat with reference to the results shown in FIG. 2, it is understood thatthe ZT values of the compound semiconductors according to Examples 1 to4 of the present disclosure show improvement over the entire temperaturemeasurement region in comparison to the compound semiconductorsaccording to Comparative Example 1 to 6.

Further, in Examples 1 to 3, the ZT values are remarkably improved, andparticularly in Example 3 where z=1.5, the ZT value is very high.

If the above results are considered together, the compoundsemiconductors of Examples 1 to 4 according to each embodiment of thepresent disclosure may have lower thermal conductivity and greater ZTvalue in comparison to the compound semiconductors according toComparative Example 1 to 6. Therefore, the compound semiconductoraccording to the embodiment of the present disclosure may be regarded ashaving excellent thermoelectric conversion and so can be very useful asa thermoelectric conversion material.

The present disclosure has been described in detail. However, it shouldbe understood that the detailed description and specific examples, whileindicating preferred embodiments of the disclosure, are given by way ofillustration only, since various changes and modifications within thespirit and scope of the disclosure will become apparent to those skilledin the art from this detailed description.

What is claimed is:
 1. A compound semiconductor, represented by ChemicalFormula 1 below: Chemical Formula 1In_(x)Co₄Sb_(12-z)Te_(z) where, in the Chemical Formula 1, 0<x≦0.5 and0.8<z≦2.
 2. The compound semiconductor according to claim 1, wherein, inChemical Formula 1, 0<x≦0.4.
 3. The compound semiconductor according toclaim 1, wherein, in Chemical Formula 1, 0<x≦0.25.
 4. The compoundsemiconductor according to claim 1, wherein, in Chemical Formula 1,0.9<z≦2.
 5. The compound semiconductor according to claim 1, wherein, inChemical Formula 1, 0.9<z≦1.75.
 6. The compound semiconductor accordingto claim 1, wherein, in Chemical Formula 1, 1.0≦z≦1.5.
 7. The compoundsemiconductor according to claim 1, wherein, in Chemical Formula 1,0.85<z≦2.
 8. The compound semiconductor according to claim 1, wherein,in Chemical Formula 1, 0.95<z≦2.
 9. The compound semiconductor accordingto claim 1, wherein, in Chemical Formula 1, 0.85<z≦1.75.
 10. Thecompound semiconductor according to claim 1, wherein, in ChemicalFormula 1, 0.95<z≦1.75.
 11. The compound semiconductor according toclaim 1, wherein, in Chemical Formula 1, z=1.5.
 12. A preparation methodof a compound semiconductor, comprising: forming a mixture containingIn, Co, Sb and Te; and thermally treating the mixture, thereby preparingthe compound semiconductor defined in claim
 1. 13. The preparationmethod of a compound semiconductor according to claim 12, wherein thethermally treating step is performed at 400° C. to 800° C.
 14. Thepreparation method of a compound semiconductor according to claim 12,wherein the thermally treating step includes at least two thermaltreatment stages.
 15. A thermoelectric conversion device, which includesthe compound semiconductor defined in claim
 1. 16. A solar cell, whichincludes the compound semiconductor defined in claim 1.